In a known manner, in a coating plant the coating head is fed with a composition commonly called "coating color". This coating color consists of the mixture and the mixing of different pigments, fillers and binders intended to impart particular visual and feel properties.
The preparation of this coating color is carried out in a mixing unit generally called a "coating kitchen". Two main techniques, differing in their principle, are generally employed for ensuring the metering and the feeding of the coating head. Thus, there is a known technique commonly called "batch", in which the various ingredients of the coating color, which are contained in specific metering hoppers, are poured in selected quantities into a mixing and storage tank. When the stirring and mixing operation is finished, the quantity of color produced is poured into the circuit connected to the coating head. The operation of preparing the color and its injection into the circuit feeding the coating head are thus independent and necessarily consecutive. It follows that the overall operation of the plant is noncontinuous, and this requires the presence of relatively costly storage stock vessels.
Furthermore, plants intended to overcome this disadvantage, which operate continuously, are also known. Thus, in this solution the various storage hoppers pour the coating ingredients directly into the circuit feeding the coating head, while they undergo mixing. Although it increases the speed of starting up the plant, this solution requires extremely accurate metering means making it possible to deliver the exact quantity of pigments or binders that are required for the quality of coating color which is adopted. These means of accurate metering increase the overall cost of a plant.
The problem which the invention is therefore intended to solve is to provide a coating kitchen allowing operation which is flexible with regard to the feeding of the coating head, which delivers a color of quality that is strictly uniform in time, and which does not require metering means that are special and of high accuracy.